V.42

What Does V.42 Mean?

V.42 is an International Telephone and Telegraph Consultative Committee (CCITT) V-series standard that regulates error-detection for high-speed modems. V.42 permits computer modems to work with both digital and analog phone lines. It’s an error-correcting procedure for data communications equipment (DCE) that uses an asynchronous-to-synchronous conversion.

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V.42 is pronounced as v-dot-forty-two.

Techopedia Explains V.42

V.42 permits receivers to request the retransmission of lost data packets, although it does not provide a guarantee about how much time it will take to deliver the error-free data to the receiving side. V.42 is generally included in dial-up modems and even includes an high-level data link control-based protocol referred to as Link Access Procedure for Modems.

The V.42 protocol includes some well-defined characteristics:

  • A non-error-correcting mode with V-series DCE, including asynchronous-to-synchronous conversion according to ITU Telecommunications Standardization Sector recommendations
  • Permits error detection using a cyclic redundancy check. Error correction is performed using the automatic retransmission of data.
  • Enables synchronous transmission through start-stop data conversion and an initial handshake in start-stop format that minimize DTE disruption

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Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.